When we reviewed Apple's iPhone OS 3.0 last year, we noted that "many users will remember it as a consistent base hitter, or 'the version that should have shipped with the first iPhone'," even though it included "extremely significant under-the-hood improvements" that mightn't be fully appreciated at first. iOS 4.0 -- the newly-renamed iPhone OS 4 -- follows the same formula. Its most obvious new features are long awaited quality-of-life improvements such as folder support that Apple would be hard pressed to charge for, alongside major but less obvious changes that dramatically improve the iPhone's and iPod touch's versatility while at least modestly enhancing their speed at certain tasks. Using a third-party app or taking pictures, for instance, may feel a little snappier though the difference won't be worthy of timing with a stopwatch; similarly, returning to the app from the Home Screen or e-mailing those pictures while doing something else will be faster, even if you don't notice it.

Perhaps as a consequence of the seemingly iterative nature of the improvements, Apple has for the first time made this full iOS upgrade free to all of its iPod touch customers, rather than charging the customary $10 fee that provoked groans in the past. Many users will be thrilled—particularly some of the iPod touch owners who held off on versions 2.0 or 3.0 in protest over the charges. But as a disappointing aside, iOS 4.0 is the first version that doesn’t run at all on the original iPod touch or iPhone, and loses certain significant features on second-generation iPod touch and iPhone 3G models, as well. In fact, it’s at least a little different on each generation of device it runs on, and has not as yet been formally announced for the iPad.

Our review of iOS 4.0 isn’t here to convince you to download or skip this major upgrade; the free pricing and new features will most likely entice you to install it on any device that’s capable of running it. But to the extent that the major new features deserve attention on both Apple’s current devices and the upcoming iPhone 4, we discuss them below for your interest. A comprehensive look at iOS 4.0’s other features is available in our Instant Expert: Secrets & Features of iOS 4 article.

1. Folders.

Folder support is tied with two other features as critically important quality-of-life additions to this version of iOS. As on most computers, an iOS folder is the same size as a standard icon, and serves as a repository for multiple applications, enabling users to eliminate or radically reduce the page-flipping that became common after Apple added support for bookmark-like “web apps” and real apps. Creating a folder is as simple as holding down on one icon for several seconds, then dragging it on top of a second icon. iOS 4 automatically makes what looks like a metal-rimmed bin with miniaturized versions of the icons inside, plus a temporary title for the folder based on the genre of the first icon you selected. You can then change the title and add or remove additional apps as you desire. Folders are automatically removed when no apps are left in a bin.

Though Apple waited way too long to add a folder system to the iPhone and iPod touch, iOS 4’s implementation of the feature is intuitive and almost entirely excellent, enabling the effective organization of numerous applications into simple categories. Tapping on any folder icon splits the screen into three parts: two faded-out views of other apps above and below a high-contrast view inside the folder’s apps. This animated look inside the folder is so attractive that it’s easy to forgive the bland-looking folder icons themselves, which rapidly transform the device’s screen into a busy-looking 5-by-4 grid with mini 3-by-3 grids inside—a future feature to switch the folder to your preferred representative icon would be great. But given how much folders improve access to apps, transforming multiple swipes into a couple of quick taps, it’s easily to love the functionality of this feature even if the look isn’t ideal.

2. Backgrounds and Redrawn Icons/Voice Memos.

Pre-iPhone phones—smartphones and non-smartphones alike—gave users the option to customize their background artwork, which Apple seemed to actively pooh-pooh in the name of clean design. Customizing the Lock Screen was as far as the company was willing to go for the iPhone’s and iPod touch’s first three years, until the iPad came along with iPhone OS 3.2 installed. Suddenly background artwork for the Home Screen was okay, and with iOS 4, the feature has come to the iPod touch 3G and iPhone 3GS. In fact, it’s more than okay for these devices: you have to go out of your way to give these devices an all-black background, as they no longer include one on their own.

Users can now select from built-in or self-supplied artwork and photographs for both the Lock Screen and Home Screen, choosing the same image or two separate images as they prefer. Apple applies dimming, drop shadowing and anti-aliasing effects to enable its own icons and text to stand out against the backgrounds, but otherwise the imagery is left unchanged in scale, positioning, and vertical orientation from the way you set it up. The Dock has been redrawn with a reflective silver glass look that matches the iPad’s and Mac’s, and icons have been given small cosmetic tweaks that modestly enhance their apparent levels of detail. Notably, the 2008 iPhone 3G and iPod touch 2G get the updated Dock design and icons, but cannot display Home Screen background wallpaper, a disappointment given that hackers have for years been able to use Home Screen backgrounds on even original iPhone and iPod touch models.

A few apps have changed, as well. The main screen of the Voice Memos application, for instance, has received a quiet redraw that shrinks the size of the holes in its classical mesh microphone artwork. Most of these changes are very minor on the current models of iPhone and iPod touch, reflecting improvements designed primarily for the higher-resolution displays of the iPhone 4 and iPad, but the Home Screen background artwork is a welcome addition—we wouldn’t be surprised if owners of iPhone and iPod touch models without support for this feature were seriously disappointed by its absence.

3. Mail.

Though it’s hard to praise in the sense that it doesn’t look very different and feels incredibly overdue—offensively so, really—a major change to the Mail application radically improves the user experience for reading e-mail messages on the go. Apple calls it the “unified inbox,” the aggregation of multiple e-mail account inboxes into a single scrolling list that’s also described as “All Inboxes,” removing your need to check separate accounts by tapping multiple times and flipping from inbox to inbox. There’s nothing more to say about this particular extremely simple-sounding feature but that it works if you want it to; otherwise, you can continue to browse inboxes individually in the old-fashioned, slower way, one-by-one. We consider this to be a huge quality-of-life improvement, but one that is so marginal from a marketing perspective that it—and similar as-yet-unimplemented features—should really appear in point releases to the iOS in the future, rather than waiting years and being touted as a major selling point.

Apple has also added an optional Threaded view to the Mail application, enabling you to view collections of e-mail in clusters representing ongoing discussions between you and other people. Threads appear as a single inbox message with a number indicating how many additional messages are part of the same discussion; clicking on the first message provides you with a list of the messages in the thread, taking you into individual messages with further taps. This feature reduces clutter within your inbox and makes it easier to see where a discussion has been going; again, it’s a welcome if not-so-flashy addition to iOS 4. We are extremely anxious to see both of these features—and further Mail improvements—make their way to the iPad, and would call them bigger real world time-savers than some of the behind-the-scenes speed improvements noted above. Mail also includes enhanced support for Google Gmail accounts, including archiving messages, another feature that will benefit some users.

4. Multitasking.

What could have been the single most significant feature in iOS 4 turns out to be something far less critical on day one to the new operating system release. For years, Apple has resisted calls to allow the iPhone and iPod touch to run multiple third-party applications at once, claiming that poor battery life and sluggish performance would follow. And to Apple’s credit, these claims were both true and not trivial to address within the iPhone and iPod touch, devices that the company engineered specifically to use relatively small battery packs and limited but power-efficient processors. The eventual solution includes new iOS 4 software—both on Apple’s end and from third-party developers—as well as new hardware. Only the 2009 iPhone 3GS and iPod touch, plus their successors and presumably the iPad, are capable of running the multitasking solution Apple eventually came up with; it’s just missing from 2007 and 2008 iPhones and iPod touch devices, including the base 8GB iPod touch model sold throughout 2009 and 2010.

Apple’s solution is an elaborate system of approximating classical multitasking using a different approach, namely using a more advanced behind-the-scenes task manager that pauses some programs in their entirety, and others only partially, enabling certain pieces of programs to continue functioning even while others are shut down. This is “real” multitasking, without equating “task” to “full application.” For the time being, third-party music streaming, voice over IP audio, and turn-by-turn GPS direction apps will be permitted to generate audio and sometimes small text alerts that overlap whatever’s running in the foreground, while other applications—ones that have been rewritten to support the new multitasking system—will largely pause and then resume when you come back to them. Pandora Radio, shown below, continues to stream audio from the company’s servers even when you’ve left the application, with a top-of-screen play icon that looks just like the iPod’s—amazingly, it even continues to stream when it’s in the middle of syncing with iTunes. Transitions between built-in and streaming music are handled through graceful, quick fades, rather than abruptly.

Some iOS 4 applications will be able to send push notification-style alerts even when the apps aren’t running, and others will be able to send “local notifications” that look like pushed messages, without the need for contact with Apple’s push servers. Via these techniques, the impact on battery life and overall system speed will be dramatically decreased relative to competing operating systems that keep entire applications idling in the background while foreground programs are running, a benefit offset by the wait and rewriting work that will be required to implement Apple’s solutions. Streaming audio continuously in the background will obviously continue to consume more power than just playing music from the integrated iPod library, but the option’s yours.

As with folder support, Apple has implemented multitasking in an almost completely excellent fashion. Double-tapping the Home button on supported iPods and iPod touches causes the screen to slide upwards, revealing a hidden panel with four initial icons inside. You can swipe on these icons to scroll rightwards through all of the open applications four at a time, tapping to switch between them, or holding down on any one of them to bring up red circles that stop the apps instantly—effectively a task manager, minus that name. Apps can also be resumed by clicking on their Home Screen icons; if they were recompiled for iOS 4, such as the application DropBox above, they come back to precisely the place they left off without the need to reload anything. The same application running on pre-iOS 4 devices can generally remember where it was, but needs to reload whatever image or document whenever the program restarts. Some apps running background processes—including third-party voice recorders such as Evernote—will display a bar at the top of the screen and continue recording even when you’re at the Home Screen. With your permission, Evernote also tracks your location for geotagging purposes, a battery-draining background process indicated by the Northeast-pointing arrow in the status bar.

Apple says that you needn’t worry about managing applications, as iOS 4 will handle all of that on its own, but it’s sometimes surprising to come back to this bar and see so many apps “running” at a given moment, seemingly waiting to be formally killed. Some apps actually are running, finishing up tasks such as sending e-mails or saving files, which may over time offer huge usability improvements to users who were accustomed to waiting out in-progress e-mails rather than moving along to doing other things. However, the list appears to persist even after restarts, suggesting that Apple’s list isn’t just for apps that are necessarily running, but also includes ones that were recently opened. If you can ignore the clutter this bar invites and just enjoy using it to switch apps, you’ll love the quickness with which you can move between apps and the nice little animated screen swapping transition effect Apple uses when you change from one to another. Next up for multitasking will be iPad implementation and possibly a way to limit the list of displayed apps such that they don’t clutter up the multitasking bar.

5. Screen Orientation Lock + iPod Controls.

Though the feature appears to be little more than an extension of the new multitasking feature, Apple has added a collection of five icons to the multitasking bar that can only be accessed by swiping all the way to the left of the currently running apps. There, you’ll find a metallic circular arrow—a Screen Orientation Lock akin to the switch on the side of the iPad, limited here solely to locking the screen in vertical portrait mode rather than horizontal mode—plus three play/pause/track buttons, and an iPod music icon that can shift to a Pandora or other streaming music icon depending on the audio app you’re running. The orientation lock merely prevents apps from switching into widescreen mode, save for features such as game or video playback that require the device to be on its side; it’s not yet as useful here as on the iPad, and similarly indicated when in use by a lock and arrow icon at the top of the screen.

The latter four buttons all replace the former iPhone OS iPod controls, which appeared some time ago as a blue text and icon overlay in the center of the screen, letting you change tracks or play/pause status from wherever else you were in Apple’s applications. While the new buttons add little to what was there before, their bottom-of-screen location and appearance are both improvements on the prior overlay Apple used, if slightly more inconvenient to reach in the name of making multitasking more usable. Overall, Apple made the right compromise here.

6. Bluetooth + Wired Keyboard Support.

One of the iPhone and iPod touch’s biggest omissions to date has been meaningful software support for their Bluetooth hardware: Apple failed to include drivers for wireless game controllers, keyboards, or even AVRCP remote button controls built into headphones, amongst other things. The company took a small step towards remedying this in iOS 4.0, carrying over the Bluetooth and wired keyboard support it introduced in iPhone OS 3.2 for the iPad—the Bluetooth part has been publicized by Apple, but the wired part has not. As a result, you can now type on the iPhone 3GS, iPhone 4 or iPod touch 3G using external Bluetooth keyboards such as Apple’s Wireless Keyboard, and—on the iPod touch—Apple’s own iPad Keyboard Dock, which has just enough room to hold the slender iPod in its narrowly-tailored dock. The iPad Keyboard Dock even works, with an uncomfortable fit, using the iPhone 3G—an iOS4 device that is not able to pair with Bluetooth keyboards. This is clear confirmation that wired keyboards are possible on all iOS 4 devices, with primarily physical rather than electronic or software incompatibility standing in the way.

But it should be noted that at least as of this moment, Apple is preventing most wired keyboard accessories from working with the iPhone and iPod touch. The iPad Camera Connection Kit works just fine with the iPad to let USB keyboards and other devices communicate with the larger-screened device, but Apple has blocked both of the Kit’s accessories from working with the iPhone and iPod touch. Hopefully, Apple won’t block other companies from developing smaller, pocketable keyboard options that don’t depend upon Bluetooth to interface with its pocket devices.

iOS 4 also supports wireless Braille devices within a new section of the VoiceOver menu within accessibility, assisting visually disabled users. Until Apple adds support for AVRCP so that headphones and other Bluetooth remote controls can change iPod music tracks wirelessly, the company’s support for Bluetooth will continue to feel unimpressive. Further, the absence of support for monaural wireless headsets on the iPod touch is at this point similarly puzzling, given that the feature is included with the iPhone; this prevents permitted VoIP applications such as Skype from using single-ear wireless accessories for listening and speaking purposes. It’s time for Apple to open up Bluetooth on all of its devices.

7. Game Center and iAd.

Two iOS 4.0 features will have significant impacts on users down the line, but are essentially inactive as of the mid-June, 2010 release date of the new operating system. Game Center is a matchmaking service for online games, enabling iPhone and iPod touch users to request each others’ presence in supported multiplayer titles, and tracking “achievements” within those games. You set up an account, a username, and a list of friends you wish to track, then can follow their accomplishments and make formal device-to-device pushed requests to play games with them. With its own standalone icon on the iPhone and iPod touch Home Screen, Game Center operates independently from and in place of third-party matchmaking, leaderboard, and achievement software released over the past two years.

iAd is a feature built by Apple to create additional revenues for itself and developers using in-app advertising that’s more compelling and powerful than what has been found in earlier iPhone and iPod touch applications. In short, iAd gives the developer a quick and easy way to insert banner-style advertisements hosted and served by Apple into their applications, with the developer receiving a cut of ad revenues based on impressions. Apple’s ads are effectively apps in and of themselves, running on iOS 4 devices without the need to exit the application a user finds them within: they can be started or stopped seamlessly without interrupting the app currently being used. iAd has been pitched as a tool to help app developers generate revenue without having to charge users higher prices; it remains to be seen how pervasive the ads will become, and whether they will tarnish the experience of using Apple’s devices, particularly given the bandwidth caps recently instituted by AT&T for new iPhone customers.

* Support for iPhoto Faces and Places organization that lets you group pictures of individual people and locations together for convenient browsing;

* Wireless note synchronization using multiple sources of notes, including Mobile Me and other e-mail accounts, enabling whatever you type in the Notes application to be instantly synchronized with your computer’s e-mail program without sending an e-mail;

* A prominent top-of-screen icon that appears when using Location Services—either the GPS hardware in iPhones or the Wi-Fi-approximated GPS in iPod touches—to signal that multitasking processes such as location trackers can currently tell where you are;

* Small tweaks to Calendar to add easy buttons to hide or show multiple calendars and birthdays;

* Replacement of the notorious “not made to work with iPhone” accessory incompatibility nag screen with a new, even less useful version, changing the Yes/No Airplane Mode option to a Dismiss button;

* An iPod app tweak that uses larger album thumbnails with numbered songs and per-song run time displays;

* A change to Mail that more conspicuously notes that you have the option to save or discard draft e-mails, such as when you’re sharing videos you watched with YouTube;

* A slightly reduced top-of-screen Safari address and search bar;

* An integrated spellchecker;

* Separate main screen calibration buttons for Nike+ running and walking; and

* New accessibility options including a Large Text feature and enhancements to VoiceOver.

With the exception of the new accessory nag screen, these new features and others, such as the addition of Microsoft’s Bing search engine as a third search option, will improve the overall user interface options of iOS 4 devices for some users. A comprehensive look at the other new features can be found in our separate article, Instant Expert: Secrets & Features of iOS 4.

9. iPhone 4-Specific Changes.

iOS 4 adds a handful of features that are specific to the as-yet-unreleased iPhone 4, including:

* Support for its quadruple-resolution “Retina Display” with far greater detail in its fonts and controls;

* Support for its now twin cameras, one front-facing with VGA resolution, and one rear-facing with 5-Megapixel resolution, 720p HD video recording and a LED flash;

* Support for FaceTime video calling over Wi-Fi between two iPhone 4 (and likely other future) devices;

* Support for gyroscope-assisted six-axis motion controls; plus

* Support for new first- and third-party iPhone 4-specific applications, including iMovie for iPhone, which are prevented from running on earlier iPhones based on hardware differences.

These features will be discussed in our separate full review of the iPhone 4.

10. iPad-Related Omissions.

Despite all of iOS 4’s additions, there are a number of iPhone OS 3.2 features from the iPad that haven’t make it onto the iPhone or iPod touch—and it’s possible that they never will. They include:

* The absence of support for fully portrait or fully landscape use, including use with the Home Button above the screen rather than below it;

* The absence of a terrain or widescreen view in Maps;

* The omission of paned widescreen modes or additional cosmetic enhancements for old iPhone and iPod touch apps, even on the high-resolution iPhone 4;

* The inability to have more than four apps in the Dock at once, except when using folders;

* The incompatibility of full-screen third-party iPad “HD” applications with iPhone 4, based in part on control and in part on text and graphic scaling issues.

Conversely, iOS 4.0 doesn’t run on the iPad at all. As of today, Apple has only said that it will bring the updated operating system to the iPad this fall. It’s currently unknown as to what new features will make the cut to the iPad, and whether the release will bring Apple’s internally-developed iPhone, iPod touch, and iPad apps into greater sync with each other. Rumors have suggested that iOS 4.1 will be the name of the fall iPad update, and that the company will bring most of the iPad features to the new iPhone and iPod touch, then vice-versa.

Conclusions

Overall, Apple’s release of iOS 4.0 follows in its predecessor’s iterative footsteps, adding features and performance boosts—obvious and non-obvious ones—that collectively make the iPhone and iPod touch families more attractive than they were last year, albeit with greater benefits for iPhone 3GS and iPod touch 3G models than 2008 iPhone 3G and iPod touch 2G versions. To the extent that this operating system update is free for every device that supports it, there’s little room to criticize its value, beyond to state that many of the features would have done a lot of good two years ago, when concerns were first being raised as to their absence. That Apple is just getting around now to adding folders and a unified inbox detracts from its ability to push decidedly ahead of competitors such as Google’s Android and Palm’s WebOS, leaving iOS behind the curve on matching its rivals’ prior year features such as Lock Screen widgets and contacts with social media hooks. That said, Apple’s implementations all reflect the sort of measured, smart approaches to problems that result from forethought and good judgment rather than a rush to implement half-baked and ultimately disappointing solutions. It’s some consolation that even if an iOS feature is very late, it’s likely to be done right.

Our praise for the overall quality of what’s in iOS 4 is tempered only by an increasing sense that Apple’s development strategy has become somewhat muddled by the release of so many different iOS devices with different screen resolutions and hardware capabilities, resulting in an unprecedented level of user confusion as to which devices are capable of running certain software. In some cases, the “capabilities” seem artificially imposed, either for marketing reasons or to compel hardware upgrades—for example, 2007-2008 iPhones and iPod touches are surely capable of displaying Home Screen artwork, and could have in iPhone OS 1.0—while in other cases, they’re based on legitimate differences in CPU power or integrated RAM, which Apple doesn’t communicate to customers at the time of purchase. The company has limited some of these issues by preserving a fairly consistent user interface across devices and treating iPhone/iPod touch applications as baby “run them in a window” versions of iPad programs, but there are still major questions as to how the iPad will handle multitasking and other iOS 4 features, as well as how developers will deal with creating apps for all of the different devices, particularly when they can’t all run the same version of iOS at the same time. For now, these issues will remain unresolved; it’s expected that Apple will address them in the very near future with the sort of thoughtfulness that went into the rest of iOS 4.

Next year, we hope to see a bolder iOS 5—one that not only brings Apple’s devices up to speed with some of the smart software features of rival platforms, but vaults ahead of them with new ideas. While free and iterative iOS updates are welcome, it would be great to see a version of Apple’s mobile operating system actually add the sort of big, Mac OS X-level UI and feature improvements that might merit actually paying for major point releases. Now that the company has worked its way through so many of the fundamental features everyone has been waiting for, perhaps that’s a possibility.

Editors' Note: iLounge only reviews products in "final" form, but many companies now change their offerings - sometimes several times - after our reviews have been published.
This iLounge article provides more information on this practice, known as revving.